First Report of Stem Canker on Phoenix Tree (Firmiana simplex) Caused by Fusarium oxysporum in China

A stem canker disease was observed on the phoenix trees located in the region of Dezhou, Shandong province. Symptomatic stems were collected and evaluated for the possible casual agent of the disease. A fungus resembling Fusarium sp. was consistently isolated from pieces of symptomatic tissues. The fungus formed abundant aerial mycelium on potato dextrose agar and produced the micro‐ and macro‐conidia on carnation leaf agar. The nucleotide sequences of the internal transcribed spacer of the rDNA from three representative isolates showed 100% identical to those of Fusarium oxysporum isolates deposited in the GenBank database. On the basis of morphological characteristics, pathogenicity test and molecular identification, the causal agent was identified as F. oxysporum. To our knowledge, this is the first report of stem canker on phoenix tree caused by F. oxysporum in China.     

Population structure and linkage disequilibrium in a large collection of Fusarium oxysporum strains analysed through iPBS markers

In the current study, 160 pathogenic strains of Fusarium oxysporum collected from tomato, eggplant and pepper were studied. Eighteen inter‐primer binding site (iPBS)‐retrotransposon primers were used, and these primers generated 205 scorable polymorphic bands. The number of polymorphic bands per primer varied between 9 and 19, with a mean of 11 bands per primer. The highest polymorphism information content (PIC) value was determined as 0.27, and the lowest was 0.05. The unweighted pair‐group method with arithmetic averages (UPGMA) dendrogram including a heat map revealed that the 160 pathogenic strains of F. oxysporum were divided into two main clusters. The first cluster mainly included F. oxysporum f. sp. capsici (FOC) and F. oxysporum f. sp. melongenae (FOMG) isolates. The second cluster mainly comprised F. oxysporum f. sp. lycopersici (FOL) and F. oxysporum f. sp. radicis lycopersici (FORL) isolates. The highest percentage of loci in significant linkage disequilibrium (LD) was detected for FOL, whereas the lowest level of LD was found for FOC, and 95.2%, 99.4%, 99.1% and 97.4% of the relative kinship estimates were less than 0.4 for FOL, FOMG, FORL and FOC, respectively. LD differences were detected among formae speciales, and LD was higher in FOL as compare to FOC species. The findings of this study confirm that iPBS‐retrotransposon markers are highly polymorphic at the intraspecific level in Fusarium spp.     

Genetic Diversity and Pathogenicity of Fusarium oxysporum f.sp. melonis Races from Different Areas of Italy

Fusarium wilt caused by Fusarium oxysporum f.sp. melonis (FOM) is a devastating disease of melon worldwide. Pathogenicity tests performed with F. oxysporum isolates obtained from Italian melon‐growing areas allowed to identify thirty‐four FOM isolates and the presence of all four races. The aims of this work were to examine genetic relatedness among FOM isolates by race determination and to perform phylogenetic analyses of identified FOM races including also other formae speciales of F. oxysporum of cucurbits. Results showed that FOM race 1,2 was the most numerous with a total of eighteen isolates, while six and nine isolates were identified as race 0 and 1, respectively, and just one isolate was assigned to race 2. Phylogenetic analysis was performed by random amplified polymorphic DNA (RAPD) profiling and by translation elongation factor‐1α (TEF‐1α) sequencing. The analysis of RAPD profiles separated FOM races into two distinct clades. Clade 1, which included races 0, 1 and 1,2, was further divided into ‘subclade a’ which grouped almost all race 1,2 isolates, and into ‘subclade b’ which included race 0 and 1 isolates. Clade 2 comprised only race 2 isolates. The phylogenetic analysis based on TEF‐1α separated FOM from the other formae speciales of F. oxysporum. Also with TEF‐1α analysis, FOM races 0, 1 and 1,2 isolates grouped in one single clade clearly separated from FOM race 2 isolates which grouped closer to F. oxysporum f.sp. cucumerinum. RAPD technique was more effective than TEF‐1α in differentiating FOM race 1,2 isolates from those belonging to the closely related races 0 and 1. Both phylogenetic analyses supported the close relationship between the three different FOM races which might imply the derivation from one another and the different origin of FOM race 2.     

Fusarium cerealis Associated with Barley Seeds in Argentina

Fusarium head blight is a fungal disease caused by a complex of Fusarium species on cereals, such as barley and wheat. It has economic impacts due to yield reductions and mycotoxin contamination. As barley production has increased considerably in the last 5 years in Argentina, a survey was conducted for identifying Fusarium species associated with barley grains. Fusarium cerealis was isolated and identified based on morphological and molecular analysis. The potential production of nivalenol and zearalenone was assessed using specific PCR assays. Koch′s postulates were carried out to confirm the pathogenicity of the fungus.     

Emergence of Antagonism Against the Pathogenic Fungus Fusarium oxysporum by Interplay Among Non‐Antagonistic Bacteria in a Hydroponics Using Multiple Parallel Mineralization

The rhizosphere microbial community in a multiple parallel mineralization (MPM) system contributes to suppression of root‐borne diseases. We hypothesized this phenomenon can be attributed to the interplay of non‐antagonistic bacteria rather than to a single antagonistic microbe. In this study, we tested this hypothesis by investigating the potential roles of bacterial interplay in a subset of MPM microbiota in the suppression of the fungal phytopathogen Fusarium oxysporum. Bacterial strains isolated from the MPM system were subjected to in vitro and in planta tests on F. oxysporum. A community of seven bacterial strains (Kaistia sp. TBD58, Sphingopyxis sp. TBD84, Bosea sp. TBD101, Ancylobacter sp. TBD132, Cupriavidus sp. TBD162, Brevibacillus sp. TBD179 and Sphingopyxis sp. TBD181) suppressed F. oxysporum growth. None of the strains alone was antagonistic against F. oxysporum, whereas several pairs of those non‐antagonistic strains inhibited its growth. Morphological observations showed the formation of swollen F. oxysporum cells in the presence of these bacterial pairs. The same bacterial pairs also suppressed Fusarium wilt disease in Arabidopsis thaliana. These results indicate that a complex bacterial interplay among non‐antagonistic bacteria can significantly contribute to the development of antagonism against F. oxysporum in the context of the MPM system.     

Genetic and virulence variation in Fusarium oxysporum f. sp. cepae causing root and basal rot of common onion in Iran

Root and basal rot of common onion (Allium cepae L.) caused by Fusarium oxysporum f. sp. cepae is one of the most important diseases causing tremendous losses in onion‐growing areas worldwide. In this study, random amplified polymorphic DNA (RAPD), intersimple sequence repeats (ISSR) and virulence studies were conducted to analyse 26 F. oxysporum f. sp. cepae isolates obtained from the main onion‐growing regions of Iran, including Fars, Azerbaijan and Isfahan states. Cluster analysis using UPGMA method for both RAPD and ISSR markers revealed no clear grouping of the isolates obtained from different geographical regions, and the isolates were observed to derive probably from the same clonal lineage. Pathogenicity test indicated that all F. oxysporum f. sp. cepae isolates were pathogenic on onion; however, virulence variability was observed among the isolates. The grouping based on virulence variability was not correlated with the results of RAPD and ISSR analyses.     

Molecular characterization of pathogenic Fusarium species in cucurbit plants from Kermanshah province, Iran

Fusarium is one of the important phytopathogenic genera of microfungi causing serious losses on cucurbit plants in Kermanshah province, the largest area of cucurbits plantation in Iran. Therefore, the objectives in this study were to isolate and identify disease-causing Fusarium spp. from infected cucurbit plants, to ascertain their pathogenicity, and to determine their phylogenetic relationships. A total of 100 Fusarium isolates were obtained from diseased cucurbit plants collected from fields in different geographic regions in Kermanshah province, Iran. According to morphological characters, all isolates were identified as Fusarium oxysporum, Fusarium proliferatum, Fusarium equiseti, Fusarium semitectum and Fusarium solani. All isolates of the five Fusarium spp. were evaluated for their pathogenicity on healthy cucumber (Cucumis sativus) and honeydew melon (Cucumis melo) seedlings in the glasshouse. F. oxysporum caused damping-off in 20–35 days on both cucurbit seedlings tested. Typical stem rot symptoms were observed within 15 days after inoculation with F. solani on both seedlings. Based on the internal transcribed spacer (ITS) regions of ribosomal DNA (rDNA) restriction fragment length polymorphism (RFLP) analysis, the five Fusarium species were divided into two major groups. In particular, isolates belonging to the F. solani species complex (FSSC) were separated into two RFLP types. Grouping among Fusarium strains derived from restriction analysis was in agreement with criteria used in morphological classification. Therefore, the PCR-ITS-RFLP method provides a simple and rapid procedure for the differentiation of Fusarium strains at species level. This is the first report on identification and pathogenicity of major plant pathogenic Fusarium spp. causing root and stem rot on cucurbits in Iran.     

Genetic Diversity of Fusarium oxysporum f.sp. lentis Population Affecting Lentil in Syria

Lentil (Lens culinaris Medik.) is an important food legume crop in Syria. Fusarium wilt (Fusarium oxysporum f.sp. lentis – Fol) is a key yield‐limiting factor in the country. The genetic diversity of Fol population was studied using 96 isolates collected from different parts of the country using molecular markers. A total of 16 markers, random amplified polymorphic DNA, simple sequence repeats and inter‐simple sequence repeats were used and 218 polymorphic markers (scorable bands) were obtained. Cluster and structure analyses grouped the isolates into three major groups and subgroups indicating high genetic diversity in the pathogen populations. The molecular variance within the population accounted 87% of the total variation indicating high diversity within population than among geographic locations. The result of this study showed that no alleles were linked to specific province, and therefore, screening for the Fusarium wilt in one location using virulent isolates could be enough to save time and resources.     

Management Fusarium wilt on melon and watermelon by Penicillium oxalicum

The potential of the biological control fungus Penicillium oxalicum to suppress wilt caused by Fusarium oxysporum f. sp. melonis and F. oxysporum f. sp. niveum on melon and watermelon, respectively, was tested under different growth conditions. The area under disease progress curve of F. oxysporum f. sp. melonis infected melon plants was significantly reduced in growth chamber and field experiments. In glasshouse experiments, it was necessary to apply P. oxalicum and dazomet in order to reduce Fusarium wilt severity in melons caused by F. oxysporum f. sp. melonis. For watermelons, we found that P. oxalicum alone reduced the area under the disease progress curve by 58% in the growth chamber experiments and 54% in the glasshouse experiments. From these results, we suggested that P. oxalicum may be effective for the management of Fusarium wilt in melon and watermelon plants.     

Morphological and Molecular Characterization of Fusarium Isolated From Maize in Syria

Maize is the third most important cereal after wheat and barley in Syria. Maize plants are attacked by several Fusarium species causing mainly stalk and ear rot of maize which poses a major impact worldwide. Identification of Fusarium species is important for disease control and for assessment of exposure risk to mycotoxines. To identify Fusarium species attacking maize in Syria, a total of 32 Fusarium isolates were recovered from maize ears collected from four different geographical regions, mainly from Ghouta surrounding Damascus. Fusarium isolates were identified based on morphology and on partial DNA sequencing of the TEF1‐α and rDNA/ITS genes. The majority (26 of 32) of these isolates was identified as F. verticillioides (subdivided into four groups), whereas three isolates turned out to be F. thapsinum, F. equiseti and F. andiyazi. The remaining three isolates were close to F. andiyazi, although further investigation is needed to confirm whether they represent a yet undescribed species. Furthermore, our results showed that sequencing the TEF1‐α gene is much more informative than sequencing of the rDNA/ITS region for Fusarium identification at the species level. PCR analysis showed that only F. verticillioides isolates were potentially fumonisin producers and that only the F. equiseti isolate was potentially trichotecene producer. This is the first report on Fusarium thapsinum, F. equiseti and F. andiyazi attacking maize in Syria.     

Transgenic tomato plants expressing a wheat endochitinase gene demonstrate enhanced resistance to <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">lycopersici</Emphasis>

Various chitinases have been shown to inhibit the growth of fungal pathogens in in vitro as well as in planta conditions. chi194, a wheat chitinases gene encoding a 33-kDa chitinase protein, was overexpressed in tomato plants (cv. Pusa Ruby) under the control of maize ubiquitin 1 promoter. The integration of transgene in tomato plants was confirmed with polymerase chain reaction (PCR) and Southern blot analysis. The inheritance of the transgene in T₁ and T₂ generations were shown by molecular analysis and the hygromycin sensitivity test. The broad range of chitinase activity was observed among the transgenic lines in T₀ and a similar range was retained in the T₁ and T₂ generations. Most importantly, the transgenic tomato lines with high chitinase activity were found to be highly resistant to the fungal pathogen Fusarium oxysporum f. sp. lycopersici. Thus, the results demonstrated that the expression of the wheat endochitinase chi194 in tomato plants confers resistance against Fusarium wilt disease caused by the fungal pathogen Fusarium oxysporum f. sp. lycopersici.     

First Report of Dieback of Mango Caused by Fusarium decemcellulare in China

During 2009–2011, a dieback disease of mango (Mangifera indica) has recently emerged on mango trees in Panzhihua City, Sichuan province of China. The disease is characterized by large irregular brown‐coloured speckles on the petioles and twigs, vascular necrosis and dry leaves and complete twig mortality. Fusarium species were isolated repeatedly from the infected petioles and twigs. The species was identified as Fusarium decemcellulare Brick based on morphology and sequence analysis of Translation Elongation Factor‐1alpha (TEF‐1α) gene. Koch's postulates were fulfilled by pathogenicity tests on potted mango seedlings. To our knowledge, this is the first record of dieback on mango caused by F. decemcellulare in China.     

First Report of Fusarium proliferatum Infecting Carnation (Dianthus caryophyllus L.) in China

In 2011, a wilt disease has been detected on carnation (Dianthus caryophyllus L.) cultivar ‘Light Pink Barbara’ in Kunming, Yunnan, China. A Fusarium sp. was consistently recovered from pieces of symptomatic tissues on Petri dishes containing potato dextrose agar (PDA). On the basis of morphological characteristics and molecular identification by DNA sequencing of ribosomal DNA internal transcribed spacer (rDNA ITS) and partial translation elongation factor‐1α (TEF) gene region, following their phylogenetic trees construction, the putative causal agent was identified as Fusarium proliferatum (Matsushima) Nirenberg, and its pathogenicity was finally confirmed by Koch's postulates. To our knowledge, this is the first report of a wilt disease caused by F. proliferatum on carnation in China.     

Genetic Diversity of Fusarium oxysporum Populations Isolated from Tomato Plants in Tunisia

Fusarium crown and root rot of tomato (Lycopersicon esculentum) caused by Fusarium oxysporum f. sp. radicis‐lycopersici is a new devastative disease of tomato greenhouse crops in Tunisia. Nothing is known neither about the population of this pathogen in this region, nor about the population of F. oxysporum f. sp. lycopersici the causal agent of Fusarium wilt of tomato. In order to examine the genetic relatedness among the F. oxysporum isolates by intergenic spacer restriction fragment length polymorphism (IGS‐RFLP) analysis and to elucidate the origin of the formae specialesradicis‐lycopersici in Tunisia by looking for genetic similarity of Tunisians isolates with isolates from a foreign source, the genetic diversity among F. oxysporum f. sp. radicis‐lycopersici and F. oxysporum f. sp. lycopersici populations was investigated. A total of 62 isolates of F. oxysporum, obtained from symptomless tomato plants, were characterized using IGS typing and pathogenicity tests on tomato plants. All Fusarium isolates were highly pathogenic on tomato. Fusarium oxysporum f. sp. radicis‐lycopersici isolates were separated into five IGS types. From the 53 F. oxysporum f. sp. radicis‐lycopersici isolates, 34 isolates have the same IGS types (IGS type 25), and the remaining 19 isolates were distributed into four IGS types. However, the only nine isolates of F. oxysporum f. sp. lycopersici have six different IGS types. This difference of diversity between the two formae speciales suggests that F. oxysporum f. sp. radicis‐lycopersici isolates have a foreign origin and may have been accidentally introduced into Tunisia.     

Fusarium Species Isolated from Common Weeds in Eggplant Fields and Symptomless Hosts of Fusarium oxysporum f. sp. melongenae in Turkey

Thirteen species of weed plants were collected between May and September in 2010 and 2011 from eggplant fields representing 11 distinct locations covering a wide geographical area of Turkey. Weeds are potential hosts of many plant pathogens and may not exhibit disease symptoms when colonized. Fusarium spp. were isolated from five monocotyledonous species and eight dicotyledonous species. A total of 212 isolates recovered from weeds were assigned to eight Fusarium species on the basis of morphological characteristics. F. oxysporum was the most frequently isolated species (29.7%), followed by F. solani (19.8%), F. graminearum (13.7%), F. verticillioides (12.7%), F.equiseti (9.9%), F. avenacearum (8.0%), F. proliferatum (3.8%) and F. subglutinans (2.4%). The F. oxysporum isolates from different weed hosts were characterized by means of pathogenicity and vegetative compatibility grouping (VCG) tests. Among these, 29 isolates were found to be pathogenic to eggplant cv. Kemer and re‐isolated as Fusarium oxysporum Schlecht. f. sp. melongenae (Fomg) as evidenced. These isolates from weed hosts were assigned to VCG 0320. This study is the first report of Fomg isolated from weeds in eggplant fields in Turkey. None of the weed species tested showed symptoms of wilting in pot experiments, and F. oxysporum was isolated with greater frequency from all inoculated weeds. The results of this study indicate that several weed plants may serve as alternative sources of inoculum for Fomg, during the growing season.     

Identification of pathogenicity‐related genes in Fusarium oxysporum f. sp. cepae

Pathogenic isolates of Fusarium oxysporum, distinguished as formae speciales (f. spp.) on the basis of their host specificity, cause crown rots, root rots and vascular wilts on many important crops worldwide. Fusarium oxysporum f. sp. cepae (FOC) is particularly problematic to onion growers worldwide and is increasing in prevalence in the UK. We characterized 31 F. oxysporum isolates collected from UK onions using pathogenicity tests, sequencing of housekeeping genes and identification of effectors. In onion seedling and bulb tests, 21 isolates were pathogenic and 10 were non‐pathogenic. The molecular characterization of these isolates, and 21 additional isolates comprising other f. spp. and different Fusarium species, was carried out by sequencing three housekeeping genes. A concatenated tree separated the F. oxysporum isolates into six clades, but did not distinguish between pathogenic and non‐pathogenic isolates. Ten putative effectors were identified within FOC, including seven Secreted In Xylem (SIX) genes first reported in F. oxysporum f. sp. lycopersici. Two highly homologous proteins with signal peptides and RxLR motifs (CRX1/CRX2) and a gene with no previously characterized domains (C5) were also identified. The presence/absence of nine of these genes was strongly related to pathogenicity against onion and all were shown to be expressed in planta. Different SIX gene complements were identified in other f. spp., but none were identified in three other Fusarium species from onion. Although the FOC SIX genes had a high level of homology with other f. spp., there were clear differences in sequences which were unique to FOC, whereas CRX1 and C5 genes appear to be largely FOC specific.     

Biocontrol of Fusarium Wilt and Growth Promotion of Tomato Plants Using Endophytic Bacteria Isolated from Solanum elaeagnifolium Stems

Seven culturable bacterial isolates, obtained from the internal stem tissues of Solanum elaeagnifolium and successfully colonizing the internal stem tissues of tomato cv. Rio Grande, were screened for their in vivo antifungal activity against Fusarium oxysporum f.sp. lycopersici (FOL) and their growth‐promoting potential on tomato plants. SV101 and SV104 isolates, assessed on pathogen‐challenged tomato plants led to a significant decrease (77–83%) in Fusarium wilt severity and vascular browning extent (76%), as compared to the inoculated and untreated control. Isolates enhanced growth parameters on pathogen‐challenged and unchallenged tomato plants. SV104 and SV101 isolates were most effective in suppressing disease and enhancing plant growth. These two isolates were identified as Bacillus sp. str. SV101 ( KU043040 ) and B. tequilensis str. SV104 ( KU976970 ). They displayed antifungal activity against FOL; pathogen growth was inhibited by 64% and an inhibition zone (11.50 and 19.75 mm) against FOL could be formed using whole cell suspensions. SV101 and SV104 extracellular metabolites also inhibited FOL growth by 20 and 55%, respectively, as compared to control. B. tequilensis str. SV104 was shown to produce protease, chitinase, pectinase, IAA and siderophores. Bacillus sp. str. SV101 displayed pectinase activity and was found to be an IAA‐producing and phosphate‐solubilizing agent. To our knowledge, this is the first study reporting on S. elaeagnifolium use as a potential source of potent biocontrol and plant growth‐promoting agents.     

Biological Control Activity of Three Trichoderma Isolates Against Fusarium Wilts of Cotton and Muskmelon and Lack of Correlation with their Lytic Enzymes

The enzymatic activity and the biocontrol ability of two new isolates of Trichoderma spp. (T-68 and Gh-2) were compared in laboratory and glasshouse experiments with a previously studied T. harzianum strain (T-35). In dual culture tests with Fusarium oxysporum f. sp. melonis and F. oxysporum f. sp. vasinfectum, isolates T-68 and Gh-2 overgrew the colonies of Fusarium, whereas T-35 failed to parasitize both wilt pathogens. Under glasshouse conditions, the three isolates of Trichoderma were effective in controlling Fusarium wilt of cotton but only T-35 was effective against F. oxysporum f. sp. melonis on muskmelon. When the three Trichoderma isolates were grown on liquid media containing laminarin, colloidal chitin or F. oxysporum f. sp. melonis cell walls as sole carbon sources, maximum β-1,3-glucanase and chitinase specific activity in the culture filtrates of all fungi was reached after 72h of incubation. When culture filtrates of the three Trichoderma isolates were incubated with freeze-dried mycelium of F. oxysporum f. sp. melonis or F. oxysporum f. sp. vasinfectum, different concentrations of glucose and N-acetyl-D-glucosamine were released. Overall no correlation was found between enzymatic activity and the biocontrol capability against Fusarium wilt on muskmelon and cotton.     

Suppression of Alfalfa Growth by Concommitant Populations of Pratylenchus penetrans and two Fusarium species

Growth of alfalfa (Medicago sativa cv. Vernal) seedlings was compared after inoculation with combinations of either Pratylenchus penetrans and Fusarium soloni or P. penetrans and F. oxysporum f. sp. medicaginis. A synergistic disease interaction occurred in alfalfa when F. oxysporum and P. penetrans were added simultaneously to the soil. Alfalfa growth was suppressed at all inoculum levels of P. penetrans and F. oxysporum, but not with F. solani. Seedlings inoculated with the nematode alone gave lower yields than when inoculated with either Fusarium species alone. Fusarium oxysporum, but not F. solani, was pathogenic to alfalfa under similar experimental conditions. Fusarium oxysporum did not alter the populations of P. penetrans in alfalfa roots, whereas the presence of F. solani was associated with a diminished number of P. penetrans in the roots.